It wasn't just Republicans, though. Nor do all Republicans think alike or desire him as their leader, for that matter.
Trump's rise to power is also largely due to the major rival party pushing a candidate that a great many people distrusted and disliked. In addition to that, another candidate - Bernie - proved to be very popular yet ended up being screwed over and a lot of his followers voted for Trump out of spite.
As with many things related to politics it is rather nuanced and far from a black or white situation. If people don't want to see another situation like Trump or Brexit then they need to stop ignoring the bigger picture.